The collection of blood from volunteer donors has become a very successful and very refined activity. The development of single needle, single use, disposable blood collection sets has provided a safe, relatively inexpensive and donor comfortable medium for use in the blood collection process. Such sets have made possible large-scale collection of blood from volunteer donors at sites such as church halls, schools or offices which might be remote from medical facilities. The availability of volunteer donors is important in that such donors tend to be relatively healthy. In addition, they provide a potentially much larger reservoir of donatable blood than is available from the available group of paid donors.
In recent years, processing of whole blood from a donor has come to routinely include separating the blood into therapeutic components. These components include red blood cells, platelets and plasma. Various techniques and apparatus have been developed to facilitate the collection of whole blood and the subsequent separation of therapeutic components therefrom.
The collection of platelets or plasma from volunteer donors, as opposed to the collection of whole blood, has not been nearly as successful. As a result, much of the plasma now collected comes from paid donors, as opposed to volunteer donors. It would be very desirable to be able to upgrade the collection of plasma so that it becomes a volunteer based activity to a much greater extent than it is currently.
Various methods are known for the collection of platelets or plasma. For example, a unit of blood can be drawn from a human donor in a conventional fashion and accumulated in a blood bag or other standard collection container. This unit of blood can then be processed by a centrifuge to separate the plasma from the other components of the blood unit. The separated platelets and plasma can subsequently be removed from the blood bag. Although allowing all blood components to be harvested, this process has the disadvantage that the donor must internally replace the complete unit of blood from which the plasma was extracted. The replacement process can take 6 to 12 weeks during which time the donor cannot again give blood. Further, this process yields only a small portion of available plasma/donor.
In a modification of the above system, plasmapheresis can be performed by centrifugation at the time of donation. The non-plasma portion of the blood is then returned to the donor immediately. While this process allows more frequent donation, often as frequently as once per week, the blood is physically separated from the donor for centrifugation.
Such physical separation is undesirable because of the cost and complexity of systems and procedures that have been developed to minimize the risk of error when several donors are being processed simultaneously. In addition, physical separation of the blood from the donor could potentially raise concerns in the collection staff of exposure to infectous agents in the collected blood if fluid drips or leaks occur.
Separation systems in which the accumulated whole blood is not physically separated from the donor are also known. These can be either batch or continuous systems.
One continuous centrifuge based system is disclosed in Judson et al. U.S. Pat. No. 3,655,123 entitled "Continuous Flow Blood Separator." The system of the Judson et al. patent uses two needles, an outflow needle and an inflow needle. Whole blood is drawn from a donor via the outflow needle. The whole blood fills a buffer bag. Blood from the buffer bag drains, under the force of gravity into a centrifuge. The system of the Judson et al. patent uses the centrifuge to separate blood components. The plasma can be collected in a container. The red blood cells can be returned to the donor via the inflow needle.
Various systems are known that utilize annular separation chambers for plasma pheresis. For example, U.S. Pat. No. 4,531,932 to Luppin et al. entitled Centrifugal Plasmapheresis Device discloses a system which incorporates a centrifuge with a rotating annular rotor. A centrally located rotating seal couples stationary fluid flow lines to the rotating rotor.
Whole blood is drained from a donor, passed through the rotating seal and subjected to separating rotational forces in the rotating rotor. Separated plasma is drawn off and concentrated whole blood cells are passed back through the rotating seal and returned to the donor.
Related types of systems which incorporate rotatable, disposable annular separation chambers coupled via rotary seals to stationary tubing members are disclosed in U.S. Pat. Nos. 4,387,848; 4,094,461; 4,007,871; and 4,010,894.
One consideration in the processing of whole blood is the requirement that the processing take place under sterile conditions. A second consideration is the requirement that processing take place so as to maximize storage life. Unless the processing takes place within a single sealed system, the permitted storage duration and usable lifetime of the blood components is substantially shortened. Components processed within a sealed system can be stored for four to six weeks or longer before use. On the other hand, whole blood or components thereof must be used within 24 hours if the system seal is broken.
To promote the desired ends of sterile processing within a single sealed system, a family of dual member centrifuges can be used to effect cell separation. One example of this type of centrifuge is disclosed in U.S. Pat. No. RE 29,738 to Adams entitled "Apparatus for Providing Energy Communication Between a Moving and a Stationary Terminal."
As is now well known, due to the characteristics of such dual member centrifuges, it is possible to rotate a container containing a fluid, such as a unit of donated blood and to withdraw a separated fluid component, such as plasma, into a stationary container, outside of the centrifuge without using rotating seals. Such container systems can be formed as closed, sterile transfer sets.
The Adams patent discloses a centrifuge having an outer rotatable member and an inner rotatable member. The inner member is positioned within and rotatably supported by the outer member.
The outer member rotates at one rotational velocity, usually called one omega, and the inner rotatable member rotates at twice the rotational velocity of the outer housing or two omega. There is thus a one omega difference in rotational speed of the two members. For purposes of this document, the term "dual member centrifuge" shall refer to centrifuges of the Adams type.
The dual member centrifuge of the Adams patent is particularly advantageous in that, as noted above no seals are needed between the container of fluid being rotated and the non-moving component collection containers. The system of the Adams patent, provides a way to process blood into components in a single, sealed, sterile system wherein whole blood from a donor can be infused into the centrifuge while the two members of the centrifuge are being rotated.
An alternate to the apparatus of the Adams patent is illustrated in U.S. Pat. No. 4,056,224 to Lolachi entitled "Flow System for Centrifugal Liquid Processing Apparatus." The system of the Lolachi patent includes a dual member centrifuge of the Adams type. The outer member of the Lolachi centrifuge is rotated by a single electric motor which is coupled to the internal rotatable housing by belts and shafts.
U.S. Pat. No. 4,108,353 to Brown entitled "Centrifugal Apparatus With Oppositely Positioned Rotational Support Means" discloses a centrifuge structure of the Adams type which includes two separate electrical motors. One electric motor is coupled by a belt to the outer member and rotates the outer member at a desired nominal rotational velocity. The second motor is carried within the rotating exterior member and rotates the inner member at the desired higher velocity, twice that of the exterior member.
U.S. Pat. No. 4,109,855 to Brown et al. entitled "Drive System For Centrifugal Processing Apparatus" discloses yet another drive system. The system of the Brown et al. patent has an outer shaft, affixed to the outer member for rotating the outer member at a selected velocity. An inner shaft, coaxial with the outer shaft, is coupled to the inner member. The inner shaft rotates the inner member at twice the rotational velocity as the outer member. A similar system is disclosed in U.S. Pat. No. 4,109,854 to Brown entitled "Centrifugal Apparatus With Outer Enclosure".
Centrifuges of the type disclosed in the above indentified Brown et al. and Brown patents can be utilized in combination with a sealed fluid flow transfer set of the type disclosed in U.S. Pat. No. 4,379,452 to DeVries. The disclosure of the DeVries patent is incorporated herein by reference. The set of the DeVries patent incorporates a blood collection container that has a somewhat elongated shape similar to those of standard blood collection sets. One embodiment of this combined system is the CS3000 cell separator system marketed by Travenol Laboratories, Inc.
The CS3000 incorporates a dual member centrifuge in combination with a sealed set of the type disclosed in DeVries. This is a continuous system that requires the donor to receive two needle punctures. Such systems have been extensively used in blood centers for plasma and platelet pheresis.
The CS3000 is a large and expensive unit that is not intended to be portable. Further, the DeVries type transfer sets are quite complex to install and use. They are also an order of magnitude more expensive than a standard, multi-container blood collection set.
A further alternate to the Adams structure is illustrated in U.S. Pat. No. 4,530,691 to Brown entitled "Centrifuge With Movable Mandrel." The specification and figures of this Brown patent are hereby incorporated by reference herein. The centrifuge of this latter Brown patent also is of the Adams-type. However, this latter centrifuge has an exterior member which is hinged for easy opening. When the hinged upper section is pivoted away from the bottom section, it carries the rotatable inner member along with it.
The inner member supports a receiving chamber with a spring biased mandrel which continually presses against a sealed, blood containing container positioned within the receiving chamber. The system of this latter Brown patent also discloses the use of two separate electric motors to rotate the inner and outer members. The motors are coupled to a control system.
There thus continues to be a need for methods and related apparatus of platelet or plasmapheresis which can readily be used with volunteer donors at various temporary locations. This method and related apparatus should be usable by technicians with a level of skill commensurate with the level of skill now found at volunteer-based blood collection centers. Further, both the method and related apparatus should be readily portable to locations such as churches or schools where blood collection centers are temporarily established. Preferably the apparatus will be essentially self-contained. Preferably, the equipment needed to practice the method will be relatively inexpensive and the blood contacting set will be disposable each time the plasma has been collected from a single donor.